1. Field of the Invention
The present invention generally relates to devices for clamping doors, panels and similar generally planar workpieces in an upright position during fitting, trimming, lock and hinge installation and similar operations, and more particularly concerns devices that are capable of holding generally planar workpieces of various sizes in an upright position and that act in an automatic manner to clamp and unclamp such workpieces.
2. Description of the Prior Art
The array of devices that may be used to clamp doors, panels and similar workpieces in an upright position includes freestanding devices that are supported by stabilizing bases such as those described by U.S. Pat. Nos. 342,187, 708,238, 771,753, 2,605,795, 2,830,632, and 3,322,422. In addition, there are clamping devices that attach to a workbench, doorframe, window sill, post or other stationary object such as those described by U.S. Pat. Nos. 1,055,937, 1,127,833, and 1,345,177. The array of devices may also be characterized as including those devices where the clamping action occurs through a pincers-type movement of the device simultaneously pressing against both sides of the workpiece, such as those described by the devices of U.S. Pat. Nos. 342,187, 771,753 and 2,605,795, and by those devices utilizing a one-side clamping movement such as those described by devices of U.S. Pat. Nos. 708,238, 1,345,177, 2,830,632, and 3,322,422. Further, the clamping of the workpiece may be accomplished in a variety ways, including a latching mechanism such as that described by the device of U.S. Pat. No. 708,238, by pressure exerted by a screw such as that described by the device of U.S. Pat. No. 1,345,177, by the weight of the workpiece such as that described by the device of U.S. Pat. No. 342,187, by a swinging jaw or jaws such as those described by the devices of U.S. Pat. Nos. 2,605,795 and 2,830,632, or by a diagonally movable jaw such as that described by the device of U.S. Pat. No. 3,322,422. Unclamping of the workpiece may be accomplished by the use of a lever such as those described by the devices of U.S. Pat. Nos. 2,830,632 and 3,322,422, by removing the weight of the workpiece as described by U.S. Pat. No. 342,187, or by manually loosening a screw or latching mechanism.
Despite the availability of such devices, there exists a need in the art for a clamping device for holding doors, panels and the like in an upright position that is capable of attachment to and use with both stationary and movable supports, is capable of automatically clamping and releasing a workpiece without the need for separate latching, clamping or releasing operations, yet is sturdy, compact, lightweight, has a minimum number of components, is easily maintained, and is inexpensive to produce.